1. Field of the Invention
The present invention relates generally to a manipulator for aerodynamic investigations of models in a wind tunnel, and more particularly to a manipulator which allows manipulation of the model by the interaction of wind within the wind tunnel and the manipulator.
2. Description of the Prior Art
Model scale information on aerodynamic characteristics may be gathered by aeroballistic or hypervelocity range tests, outdoor free fight tests, spin tunnel experiments or dynamic experiments in wind tunnels. These tests are mainly used for visual studies of the air flow characteristics and the forces of the aircraft model. Generally, the preferred method of testing incorporates the use of a wind tunnel. A model may be either a captive model, i.e., mechanically secured to a mounting platform or support arm, or a free model.
Future aircraft designs will include the capability to maneuver under extreme conditions, where conventional aerodynamic controls are not sufficient. Such "post stall" maneuvering concepts envision finite rate, asymmetric flow interactions to improve pointing and evasion capability. Many of the new flow interactions and opportunities cannot yet be flight tested because existing aircraft technology does not permit such maneuvers to take place. Devices presently used to perform simulations of maneuvers in the wind tunnel are massive and designed for specific motions, and are unsuitable for all but the easiest of maneuvers.
This application deals mainly with captive models. Known simulators for aerodynamic investigations of captive models in a wind tunnel include a multipart support arm, the parts of which are mounted in relation to each other by means of bearings. The support arm is adjusted by a spindle transmission system, electric motors or positioning cylinders to provide motion to the captive model. Generally, these simulators are restricted to at most two degrees of freedom. The following U.S. Patents illustrate various constructions for support arms and other wind tunnel equipment which imparts motion to a model.
U.S. Pat. No. 4,688,421, by Pzsolla, discloses a rear support balance body which is utilized in a wind tunnel. The balance body is composed of an action beam and a reaction beam. The balance body is inserted between a model and a mounting for the model.
U.S. Pat. No. 4,658,635, by Pzsolla et al., discloses a simulator for aerodynamic tests in a wind tunnel. Linear cylinders are provided to generate motion of the model.
U.S. Pat. No. 4,475,385, by Farmer, discloses a model mounting system which provides motion via a tunable mounting plate.
U.S. Pat. No. 4,116,056, by Bulychev et al., discloses a mounting system for aerodynamic models which utilizes a plurality of elastic suspension lines. A hoisting mechanism is attached to the suspension lines and provides motion to the model.
U.S. Pat. No. 4,112,752, by Hafner et al., discloses an apparatus for measuring force components upon aerodynamic models. The device includes three orthogonally disposed bearing members which provide motion to the model.
U.S. Pat. No. 4,091,665, by Fletcher et al., discloses a wind tunnel reaction control model block. The block includes a plurality of thrusting nozzles which may be configured in various combinations to simulate particular thrust characteristics.
U.S. Pat. No. 4,107,986, by Jones, discloses a strain gage balance having fixed beams upon which strain gages are attached.
U.S. Pat. No. 4,074,567, by Horanoff, discloses a wind tunnel balance. This balance utilizes deflection beams to reduce the interaction between the beam and an air flow in a wind tunnel. The deflection beams do not provide any movement to a model within the wind tunnel.
U.S. Pat. No. 4,033,185, by McNally et al., discloses a wind tunnel simulator in which gas is forced through fixed passageways to interact with a tracer projectile. A motor is provided to impart motion to the projectile.
U.S. Pat. No. 3,866,467, by Horanoff, discloses a model support which utilizes a spherical air bearing and a plurality fiber optic cables associated with the air bearing for determining the relative position of the bearing and associated model.
U.S. Pat. No. 3,695,101, by Hanson, discloses a lift balance device. Static lift forces are balanced by the flow of pressurized air against a piston which slides loosely in a casing. This lift is measured by piston displacement.
U.S. Pat. No. 3,613,443, by Curry, discloses a large scale external balance which supports a model in a wind tunnel via a strut which is affixed to the floor of the wind tunnel.
U.S. Pat. No. 3,587,306, by Bryan, discloses a dampening system which is utilized in a wind tunnel.
U.S. Pat. No. 3,561,264, by Needham et al., discloses a link for connecting a model frame to a subframe which is attached to a wind tunnel floor.
U.S. Pat. No. 3,554,028, by Horanoff, discloses a pitch damping balance which utilizes a piston cylinder sliding cam mechanism to impart motion to a model mounted upon the balance.
U.S. Pat. No. 3,552,201, by Horanoff, discloses a roll moment balance. A fixed canted fin assembly is provided on the aft end of a model to impart rotational motion to the model and thus enable a roll moment to be determined.
U.S. Pat. No. 3,456,503, by Wise, discloses a free flight model launch assembly. This device utilizes a turbine for generating an initial spin on the model before launch.
U.S. Pat. No. 3,447,369, by Horanoff, discloses a model support structure which incorporates an air turbine. The air turbine is utilized to provide spin to the model.
For further information on wind tunnel design and captive model testing, please see:
"Rotary Balance Testing of Aircraft Dynamics", Report of Fluid Dynamics Panel Working Group 11, AGRAD Advisory Report No. 265; and PA1 "A Review of Techniques for Determination of Dynamic Stability Parameters in Wind Tunnels", AGRAD-LS-114, (1981).
The most obvious objective of simulating complex maneuvers is to explore the flow phenomena and forces which occur in the course of the motion. A second objective, subordinate to the first, is to turn a transient, one time maneuver into an event that can be precisely duplicated periodically. This would convert the transient flow measurement problem into periodic problem, amenable to advanced diagnostic systems which are now used in rotorcraft and compressor flows. When the rates of motion are converted from the full-scale flight environment to the equivalent rates for scale models in a wind tunnel, it is found that the rates are quite high and require large forces and moments. If the manipulator must perform these maneuvers independent of the aerodynamic forces acting on the model, a large, rigid manipulator arm is required. The aerodynamic forces and the large mass of the manipulator, even if economically feasible, becomes too massive in relation to the model and produces unacceptable flow interference in the wind tunnel. Thus, the manipulators described above would be incapable of performing these maneuvers.